He apologized to riders and said the ferry system is fragile and vulnerable to disruptions due to an aging fleet and deferred maintenance.

Service has been troubled since Tuesday, when the ferry MV Tacoma lost power on the busy Seattle-Bainbridge Island route and a ferry was shifted from the Edmonds-Kingston route, causing delays for those riders.

No estimate was available for the return of the Tacoma, which has an electrical problem, Capacci said.

Service should return to normal this weekend with the return of the MV Wenatchee, which has been in dry dock in Vancouver, B.C., to repair a leak.

As part of the shuffle, service was canceled Thursday and today on the run between Anacortes and Sidney, B.C. That boat was sent to restore two-boat service on the Edmonds-Kingston run.

The system had little flexibility because the MV Yakima is out for motor maintenance and the MV Kitsap for painting, Capacci said.

Washington State Ferries operates 22 vessels — the largest such fleet in the U.S. — on 10 routes across Puget Sound.

State ferries carry more than 23 million commuters, tourists and business passengers a year.

The state is in the process of adding three Olympic-class ferries.

The MV Tokitae is in service. Another vessel is under construction, and one is planned.

The state Transportation Department also is in the process of finding a permanent ferry system director to replace David Moseley, who resigned in April.